@Groomp
Kai clearly developed some rather strong issues after finding his best friend's tortured and disemboweled corpse chained up in the air by a sociopath. He didn't have any friends left on the outside either, since they all went to juvie, so he kept it all to himself. He seems flippant at times, but to me that seems like an act. Him and his Kyoranki pals are all morons though, blaming Meguro for just doing his part as guard. He was just a junior gangbanger, doing his job. Sure, Jousuke was utter scum (if due to his own traumas), but it was up to the older ranks (the current Kyoranki, since the 5th gen leadership couldn't be depended on) to do something about that. Blaming Meguro, a junior, for not betraying his boss at the drop of a hat when confronted, is stupid.
I'm betting the reason Tanzawa and the rest "framed" Kyoranki is because they simply wanted to put the war and murders behind them. If Kyoranki hadn't gone to juvie, the police would have kept investigating for a long, long time, and Kyoranki did allow Jousuke to commit a sleeve of murders, mutilations and tortures before they begun plotting to betray him.